1. Field of the Invention
The present invention relates to semiconductor memory devices and, more particularly to a semiconductor memory device having a function of performing a burn-in test in a molded state.
2. Description of the Background Art
Conventionally, a burn-in test has been used for testing a memory device. In the burn-in test, a stress is applied to the device to determine its reliability.
As a storage capacity of the memory device increases, the time required for the burn-in test to apply stresses to word lines also increases. For example, while a 64-M SDRAM (a Synchronous Dynamic Random Access Memory) has 4096 word lines in total, a 256-M SDRAM has as many as 8192 word lines.
In the conventional test method, a stress has been applied to one word line at a time. However, to apply the stress to the 256-M SDRAM which is equal to the stress applied to 64-M SDRAM, twice as much burn-in time is required.
In addition, under conventional semiconductor memory device is not provided with a function of investigating the cause of malfunction.
Therefore, it is required that the test is efficiently and correctly performed in a reduced amount of time. To clearly investigate the device, a detailed test program must efficiently be performed.